Data frames used in wirelessly communicating over various communication channels according to the third Generation Partnership Program (3GPP) (e.g. over the channels DCH, DSCH, HS-DSCH, RACH, FACH, and others) are prescribed by various 3GPP technical specifications for frame protocols—in particular, TS25.425, TS25.427 and TS25.435—each of which provides for a so-called Spare Extension (SE) IE (information element), i.e. each provides/specifies a location (a field) where an IE can be added to (specified for) a frame in later releases of the 3GPP technical specifications without making the frame incompatible with currently specified frames. For example, TS25.435 v5.5.0 specifies a location where 0-2 octets are reserved for future use (for one or more to-be-defined IEs). The SE section is provided for all releases from release '99 and later. Any fields added after so-called release '99 (to later versions of release '99 or to later releases) are added to the SE section.
Due to the lack of definition regarding the SE—i.e. due to lack of a specification as to how to use the SE in the 3GPP specifications for adding new IEs for a specification release (i.e. e.g. Rel-5 or Rel-6)—it is difficult to use the SE in practice. For one thing, it is hard to detect whether a SE is in use since to do so a receiving node must parse all the IEs in the payload part of a frame in order to find out if a SE is present, and even if the receiving node finds and extracts an SE part, it is hard for the receiving node to determine how the SE is used—i.e. it is hard to know, in case of more than one new IE being provided via the SE, in what order the IEs occur in the frame—since how to use it is not defined. For example, if an IE is added in Rel-6 and the Rel-6 specification is frozen, it is then hard to know how to add an IE to Rel-5 in case there is a critical error in the Rel-5 specification, necessitating a new IE. To understand this, refer to FIG. 2, which shows the Frame Structure, and then refer to FIGS. 3A and 3B, which illustrate that if we add an IE in the SE in Rel-6 and then freeze the specification, it is hard to know where to add a new IE in Rel-5 to correct a critical error.
One thing is for sure, though: where the new Rel-5 IE is added can have consequences. If we add the new Rel-5 IE in front of the Rel-6 IE for example, it will cause a change in the Rel-6 specification that is not backward compatible. If we add the new Rel-5 IE after the Rel-6 IE, then a Rel-5 implementation could also understand the Rel-6 IE.
Thus the invention addresses how to use the SE—i.e. how to add new IEs for a release and especially so as to accommodate earlier releases—and also addresses how to indicate whether the SE is in use.
Additionally, while the maximum size of the SEF in the control frames in the various above-mentioned frame protocols (i.e. those of TS25.425, TS25.427 and TS25.435) is 32 octets, the maximum size of the SEF in the protocols is only 2 octets, although there is perhaps no good reason for the difference in length. Such a small data frame spare extension can prove to be problematic because of overly restricting the SE. Thus the invention also addresses the length of the SE in data frames according to the above protocols.